1. School of Chemistry and Physics, University of KwaZulu-Natal, Scottsville, Pietermaritzburg, South Africa;
2. Department of Pure and Applied Chemistry, Masinde Muliro University of Science and Technology, Kakamega, Kenya;
3. School of Science, College of Science and Technology, University of Rwanda, Kigali, Rwanda;
4. Department of Chemistry, Faculty of Applied Sciences, Durban University of Technology, Durban, South Africa